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United States Patent |
5,032,291
|
Sublette
|
July 16, 1991
|
Catalytic reduction of nitro- and nitroso- substituted compounds
Abstract
A process is disclosed for treating water or solids contaminated with a
nitro- or nitroso- substituted compound comprising reducing a nitro- or
nitroso- substituted compound in the presence of an effective catalytic
amount of at least one of a corrin- or porphyrin- metal complex. The
present invention is particularly useful in treating waste water or soil
contaminated with nitro- or nitroso- substituted compounds.
Inventors:
|
Sublette; Kerry L. (Tulsa, OK)
|
Assignee:
|
ABB Environmental Services Inc. (Portland, ME)
|
Appl. No.:
|
542101 |
Filed:
|
June 22, 1990 |
Current U.S. Class: |
210/757; 210/903; 405/128.75; 588/319; 588/403; 588/408; 588/409 |
Intern'l Class: |
C02F 001/70 |
Field of Search: |
210/757,903
405/128
423/DIG. 20
|
References Cited
U.S. Patent Documents
4219419 | Aug., 1980 | Sweeny | 210/754.
|
4323515 | Apr., 1982 | Cognion et al. | 560/342.
|
Foreign Patent Documents |
8810944 | May., 1988 | GB.
| |
Primary Examiner: Hruskoci; Peter
Assistant Examiner: Shideler; Krisanne
Attorney, Agent or Firm: Olstein; Elliot M., Lillie; Raymond J.
Claims
What is claimed is:
1. A process for treating water or solids contaminated with at least one
nitro- or nitroso- substituted compound, comprising:
reducing said at least one nitro- or nitroso- substituted compound in the
presence of an effective catalytic amount of at least one of a corrin- or
porphyrin metal complex.
2. The process of claim 1 wherein the metal portion of said complex is a
metal ion selected from Group IIa, Group IIIa, Group IVa, Group Va, Group
VIa, Group VIIa, Group VIII, Group Ib, Group IIb, Group IIIb, and the
Lanthanide and Actinide Series of the Periodic Table.
3. The process of claim 2 wherein said metal ion is selected from the class
consisting of Co.sup.+2, Fe.sup.+3, Fe.sup.+2, Ni.sup.+2, Mo.sup.+3,
V.sup.+5, Ca.sup.+2, Ba.sup.+2, Sr.sup.+2, Cr.sup.+3, Cr.sup.+5,
Cu.sup.+2, Mn.sup.+2, and Zn.sup.+2.
4. The process of claim 3 wherein said metal ion is Co.sup.+2.
5. The process of claim 1 wherein said reducing takes place in the presence
of a reducing agent.
6. The process of claim 5 wherein said reducing agent is selected from the
class consisting of dithiothreitol, dithioerythreitol, mercaptans,
mercaptosugars, borohydrides, dithionites, sulfites, phosphites,
hypophosphites, and sulfides.
7. The process of claim 6 wherein said reducing agent is dithiothreitol.
8. The process of claim 5 wherein said reducing of said at least one
nitro-and/or nitroso- substituted compound with said reducing agent in the
presence of a catalyst takes place in an aqueous solution.
9. The process of claim 1 wherein said complex is a porphyrin- metal
complex.
10. The process of claim 9 wherein said porphyrin is selected from the
group consisting of hematoporphyrin, protoporphyrin, uroporphyrin, and
coproporphyrin.
11. The process of claim 10 wherein said porphyrin is hematoporphyrin.
12. The process of claim 1 wherein said complex is a corrin.
13. The process of claim 12 wherein said corrin is selected from the class
consisting of vitamin B.sub.12, vitamin B.sub.12b, and vitamin B.sub.12C.
14. The process of claim 1 wherein said at least one nitro- or nitroso-
substituted compound is trinitrotoluene.
15. The process of claim 1 wherein said at least one nitro- or nitroso-
substituted compound is 1, 3, 5-trinitrohexanhydro- 1, 3, 5-triazine.
16. The process of claim 1 wherein said at least one nitro- or nitroso-
substituted compound is a nitrotoluene.
17. The process of claim 1 wherein said at least one nitro- or nitroso-
substituted compound is a dinitrololuene.
Description
This invention relates to the reduction of nitro and/or nitroso
substituents of organic molecules to amino substituents. More
particularly, this invention relates to the reduction of such nitro and
nitroso substituents to amino substituents in the presence of a catalyst
comprising a metal ion and a complexing agent.
Nitrosubstituted organic compounds are commonly associated with dye,
pesticide, and munitions wastes. Such compounds are environmentally
persistent and toxic, especially to marine life.
For example, during the processing of trinitrotoluene (TNT), about 4.5% of
the crude product comprises objectionable unsymmetrical TNT isomers which
must be removed to achieve suitable properties for military use. The
removal of such isomers is done typically by treatment of the crude
product with aqueous sodium sulfite. The sodium sulfite reacts with
unsymmetrical TNT isomers to produce water soluble sulfonates are removed
with the spent sulfite solution. The sulfonated nitrobodies in the waste
water stream are highly toxic, and when dry, can represent an explosion
hazard.
In accordance with an aspect of the present invention, there is provided a
process for treating water or solids contaminated with at least one nitro-
or nitroso- substituted compound comprising reducing the at least one
nitro- or nitroso-substituted compound in the presence of an effective
catalytic amount of at least one of a corrin- or porphyrin- metal complex.
In one embodiment, the metal portion of the complex may be a metal ion
selected from Group IIa, Group IIIa, Group IVa, Group Va, Group VIa, Group
VIIa, Group VIII, Group Ib, Group IIb, or Group IIIb, or the Lathanide or
Actinide Series of the Periodic Table. Preferably, the metal ion which is
complexed in the catalyst may be selected from the group consisting of
Co.sup.+2, Fe.sup.+3, Fe.sup.+2, Ni.sup.+2, Mo.sup.+3, V.sup.+5,
Ca.sup.+2, Ba.sup.+2, Sr.sup.+2, Cr.sup.+3, Cr.sup.+5, Mn.sup.+2, and
Zn.sup.+2. The complexed metal ion may also be complexed with an
additional ligand. The ligand may be an anion such as cyanide, sulfite,
phosphate, thiocyanate, thiosulfate, or perchlorate. The ligand also may
be a polar neutral molecule such as CO or H.sub.2 S.
Porphyrins and corrins are large, cyclic, metal-chelating molecules of
similar structure, with porphyrins containing the ring system (1), and
corrins containing the ring system (2):
##STR1##
In these systems the two `central` hydrogen atoms bonded to the nitrogen
may be replaced by a single coordinated metal ion to form complexes of the
structures (1A) and (2A) below, where M is a metal ion:
##STR2##
Substituent groups may also be present on the peripheral substitution
positions of these ring systems, and the metal ion M may be coordinated to
additional ligands such as those hereinabove described.
The porphyrin may include --COOH groups or other polar ionizable functional
groups on the periphery of the porphyrin ring or, alternatively, one or
more of the --COOH groups on the porphyrin ring may be replaced by
--COONR.sub.1 R.sub.2 groups where R.sub.1 and R.sub.2 are independently
alkyl or hydrogen, or salts thereof with a counter cation. The
introduction of other functional groups onto the periphery of the
porphyrin ring for the purpose of changing solubility properties,
facilitating immobilization on a solid support or binding to soils or
other natural solid substrates is included within the scope of the present
invention.
Porphyrins and corrins are found in nature; for example, hemoglobin and
chlorophyll, where M is iron and magnesium respectively, are porphyrins.
Corrins are for example found in nature as vitamins B12 (cyanocobalamin),
B12b (hydroxocobalamin) and B12c (nitrosocobalamin), each of which
contains a cobalt ion at the ring centre.
Cyanocobalamin, for example, is of the following structure:
##STR3##
Porphyrins which may be employed include hematoporphyrin, protoporphyrin,
uroporphyrin, and coproporphyrin.
Metal ions which may be complexed with the porphyrins or corrins
hereinabove described include those selected from Group IIa, Group IIIa,
Grou IVa, Group Va, Group VIa, Group IIa, Group VIII, Group Ib, Group IIb,
Group IIIb, or the Lanthanide or Actinide Series of the Periodic Table.
Particularly preferred metal ions are those selected from the group
consisting of Co.sup.+2, Fe.sup.+3, Fe.sup.+2, Ni.sup.+2, Mo.sup.+3,
V.sup.+5, Ca.sup.+2, Ba.sup.+2, Sr.sup.+2, Cr.sup.+3, Cr.sup.+5,
Cu.sup.+2, Mn.sup.+2, and Zn.sup.+2, with Co.sup.+2 being particularly
preferred.
Particularly preferred catalysts are complexes of hematoporphyrin with
cobalt. The chelated, or complexed Co.sup.+2 ion may be additionally
complexed with a ligand comprising an anion or polar neutral molecule as
hereinabove described.
When a corrin is employed as the complexing agent, the corrin ring may
include one or more substituents of the formula (CH.sub.2 CH.sub.2).sub.n
COX, wherein n is from 0 to 3, and X is --OH, or NR.sub.1 R.sub.2, wherein
R.sub.1 and R.sub.2 are independently alkyl or hydrogen, and when X is
--OH, the --COOH group may be present in an ionized from with a counter
cation.
The introduction of any other functional group on the periphery of the
carrier ring for the purpose of changing solubility, facilitating
immobilization on a solid support or binding to soils or other natural
solid substrates is also included within the scope of the present
invention.
The porphyrin complexes may be prepared by incubating together in aqueous
solution the porphyrin (free of a complexed metal ion) and the metal ion
to be complexed, preferably in a equimolar ratio, and with an equimolar
amount of the ligand if desired. For coproporphyrin, uroporphyrin,
protoporphyrin and hematoporphyrin, a solution of pH 9 (Tris/HCl buffer)
and a chloride counter anion for the metal ion is suitable. In the
alkaline (pH 9) conditions referred to above, the carboxylic acid groups
on the porphyrin substitution positions may be ionized so that the complex
may be present in solution as a carboxylate anion.
The corrin complexes may be prepared, for example, by reaction in solution
together of the ligand L and a corrinoid precursor containing the
following cyanometal-centered ring system:
##STR4##
in which L' represents either an unoccupied coordination site on the metal
ion, or represents a ligand which may easily be displaced by the ligand L.
In one embodiment, the precursor is cyanocobalamin itself, in which case M
is cobalt and the ligand L consists of the residue of the chelating
substituent chain of cyanocobalamin shown hereinabove. This chain is
easily displaced by ligands such as for example cyanide, perchlorate,
thiocyanate, thiosulphate and sulphite. Cyanocobalamin may also be used to
prepare precursors of the cyanometal-centered ring hereinabove described,
in which M is other than cobalt, by reacting a solution of cyanocobalamin
with a chelating ligand which has a stronger affinity for cobalt than the
cyanocobalamin residue, such as EDTA, preferably to form an insoluble
cobalt-chelating ligand complex which may easily be separated. This leaves
a vacant co-ordination site in the centre of the corrin ring into which a
metal ion may be inserted by incubating the corrin with a soluble salt of
the desired metal (usually a metal chloride). The metal ion may be
selected from those hereinabove described. An additional ligand, such as
an anion or polar neutral molecule as hereinabove described may be added
to the complex by incubating the complex with the anion or polar neutral
molecule.
Suitable conditions for preparation of the complex from a corrinoid
precursor are reaction of the precursor, for example cyanocobalamin, with
an equimolar amount of the ligand (and a suitable counter-ion if
necessary, for example an alkali metal) in aqueous solution.
The porphyrin and corrin complexes may be prepared at a temperature of
about 37.degree. C. and preferably in the dark. The concentration of
porphyrin, metal and ligand (if used), or of corrinoid precursor and
ligand do not appear to be critical, but a convenient concentration is
about 0.2 mM each. Under these conditions useful amounts of the complex
may be formed in about 30 minutes. The complex may then be isolated from
solution using conventional methods, or may be stored in solution,
preferably in the dark.
In another method of preparation, the porphyrin or corrin complex or the
corrinoid precursor may be prepared by a microbiological process; i.e., by
culturing a suitable microorganism which produces or secretes the complex
or precursor of the complex, and then harvesting these from the culture
medium using known harvesting methods.
The porphyrin and corrin complexes used in the method of the present
invention may, in some cases, have one or more functional substituents
such as amine, amide, hydroxy, azo, and acid groups, and may in some cases
have a complex stereochemistry. Thus, the complexes may exist in a number
of ionized or protonated forms depending upon the pH, etc., of the medium
in which they are contained, and may also exist in a number of complexed
forms or in an ionized form combined with a counterion. The complexes may
also exist in a number of forms which differ only in the spatial
arrangement of functional groups. The method of the invention includes all
such forms of the complex, and all stereoisomeric forms thereof.
It is also contemplated that the porphyrin- or corrin- metal complex may be
immobilized on a solid support such as activated carbon, diatomaceous
earth, or glass.
The process of the present invention may take place in the presence of a
reducing agent. The reducing agent may be an organic or an inorganic
reducing agent. Organic reducing agents include dithiothreitol,
dithioerythreitol, mercaptans, and mercaptosugars. Inorganic reducing
agents include borohydrides, dithionites, sulfites, phosphites,
hypophosphites, and sulfide. Alternatively, in complex environments such
as anaerobic soils and sediments, at sufficiently low redox potentials
naturally occurring reducing agents are available. A preferred reducing
agent is dithiothreitol.
Although the scope of the present invention is not to be limited to any
theoretical reasoning, it is believed that the reducing agent is an
electron source, and the catalyst is a conveyor of electrons to the nitro-
and nitroso- compounds.
The method of the present invention may be used in conjunction with the
reduction of various nitro-substituted or nitroso-substituted organic
molecules to amino-substituted molecules. Such compounds include, but are
not limited to, trinitrotoluene (TNT), 1,3,5,
-trinitrohexanhydro-1,3,5-triazine (RDX), dinitrotoluenes, and
nitrotoluenes. The dinitrotoluenes and trinitrotoluenes may by symmetrical
or asymmetrical. The asymmetrical dinitro- or trinitrotoluenes may be
sulfonated. Preferably, the method of the present invention is carried out
in an aqueous environment, such as an aqueous solution.
The present invention is particularly applicable to the treatment of waste
water or soil that is contaminated with nitro-and/or nitroso- substituted
compounds, whereby such compounds are reduced in the presence of the
catalyst hereinabove described.
A particular example of the application of the method of the present
invention is the pre-treatment of waste water streams generated by
munitions plants ("pink water") so as to render the waste water amenable
to conventional biological waste treatment such as activated sludge
treatment. In particular, the method of the present invention may be
employed to convert the primary components of pink water, TNT and RDX to
less biologically recalcitrant species as a preparation for biological
mineralization. The method of the present invention may also be used to
treat soil contaminated with nitro- and/or nitroso-substituted organic
compounds. It is to be understood, however, that the method of the present
invention is not limited to such processes.
The invention will be further described with respect to the following
examples; however, the scope of the invention is not to be limited
thereby.
EXAMPLE 1
A Co.sup.+2 -hematoporphyrin complex was prepared as follows: 1.5 mg of
hematoporphyrin was dissolved in 15 ml of 100 mM Tris buffer, pH 9.0. To
this solution was added an equal volume of equimolar CoCl.sub.2. The
resulting mixture was then incubated at 37.degree. C. for 30 min. in the
dark. This solution was then used as a source of Co.sup.+2
-hematoporphyrin.
4-nitrotoluene and 2-nitrotoluene have been used as model compounds for the
nitrosubstituted components of pink water. Reaction mixtures were
typically prepared as follows:
20 ml of Tris buffer (pH 9.0) was saturated with 2-nitrotoluene or
4-nitrotoluene by sonication at 40.degree. C. for 1 hour. At the end of
this time the solution was cooled to room temperature and the organic and
aqueous phases separated. The aqueous phase was assumed to be saturated
and corresponded to roughly 400-500 ppm nitrotoluene.
Dithiothreitol was used as reducing agent or ultimate source of electrons.
0.8-3.2 mg/ml dithiothreitol was added to this saturated nitrotoluene
solution with mixing.
The reaction was initiated by addition of 0.4 ml of the Co.sup.+2
-hematoporphyrin solution described above. The reaction mixture was then
quickly dispensed in 2 ml portions to test tubes, purged with nitrogen and
incubated at 37.degree. C.
Controls were prepared as above, but without the addition of the Co.sup.+2
-hematoporphyrin solution.
At intervals the reaction was stopped in one or more test tubes by
extraction with hexane. Extracts were analyzed by gas chromatogrpahy (HP
5890) with mass spectrometer detector. The chromatographic conditions
were:
Column: HP-1 (crosslinked methyl silicone gum-12 m.times.0.2 mm.times.0.33
.mu.m film thickness)
Carrier Gas: Helium
Temperature Profile:
Initial temp. 40.degree. C. (5 min.)
Rate 5.degree. C./min.
Final temp. 250.degree. C. (12 min.)
Injection Port Temperature: 250.degree. C.
Transfer Line Temperature: 200.degree. C.
Under these conditions the following retention times were observed:
______________________________________
Compound Retention Time (min.)
______________________________________
2-nitrotoluene
12.8
2-aminotoluene
10.4
2-nitrosotoluene
8.0
4-nitrotoluene
14.4
4-aminotoluene
10.3
4-nitrosotoluene
8.5
______________________________________
The following pertinent observations were made in these experiments:
At a dithiothreitol concentration of 3.2 mg/ml, 4-nitrotoluene was
completely converted to 4-aminotoluene in less than 10 minutes. At lower
concentrations of the reducing agent (1.6 mg/ml), conversion was slower
with the accumulation of 4-nitrosotoluene as well as 4-aminotoluene in the
reaction mixture.
Conversion of 2-nitrotoluene was slower than that of 4-nitrotoluene at the
same concentration of reducing agent. 2-nitrosotoluene was seen as an
intermediate in the reduction of 2-nitrotoluene to 2-aminotoluene.
The above example indicates the ability of Co.sup.+2 -porphyrin complexes
to catalyze the reduction of nitro- or nitrososubstituted toluenes to the
corresponding anilines. The rate of reaction is dependent upon the
structure of the nitro or nitrososubstituted compound, the concentration
of the reducing agent, the concentration of the complex as well as pH,
temperature, etc. The example also indicates that the corresponding
nitroso- compounds will accumulate when reaction rates are low or when the
reducing agent concentration is limiting. Thus, under actual operating
conditions, the contaminated material (waste water, soil, etc.) should be
tested to determine the reducing agent concentration required for complete
conversion at an acceptable residence time if the nitroso intermediate is
particularly toxic or biologically recalcitrant.
EXAMPLE 2
A Co.sup.+2 -hematoporphyrin complex was prepared as follows: 1.5 mg of
hematoporphyrin was dissolved in 15 ml of 100 mM Tris buffer, pH 9.0. To
this solution was added an equal volume of equimolar CoCl.sub.2. The
resulting mixture was then incubated at 37.degree. C. for 30 min. in the
dark. This solution was then used as a source of Co.sup.+2
-hematoporphyrin.
In this example, 2,4-dinitrotoluene has been used as a model compound of
the nitrosubstituted components of pink water. Reaction mixtures were
typically prepared as follows:
1.0 ml of Tris buffer (pH 9.0) was saturated and corresponded to roughly
400-500 ppm of 2,4-dinitrotoluene.
Dithiothreitol was used as a reducing agent or ultimate source of
electrons. 0.8-3.2 mg/ml dithiothreitol was added to this saturated
2,4-dinitrotoluene solution with mixing.
The reaction was initiated by addition of 0.5 ml of the Co.sup.+2
-hematoporphyrin solution described above. The reaction mixture was then
purged with nitrogen and incubated at 37.degree. C.
Controls were prepared as above, but without the addition of Co.sup.+2
-hematoporphyrin solution.
At intervals, samples of the reaction mixtures were analyzed by high
performance liquid chromatography (HPLC) using an HP 1090L HPLC with a
10-cm.times.2.5-mm Hypersil 5.mu. column. At a dithiothreitol
concentration of 3.2 mg/ml, 2,4-dinitrotoluene completely disappeared from
the reaction mixture within 10-15 min. 1-Methyl-4-nitroaniline and
2-nitro-3-methylaniline were identified as reaction intermediates;
however, the ultimate reaction product was 2,4-diaminotoluene.
It is to be understood, however, that the scope of the present invention is
not to be limited to the specific embodiments described above. The
invention may be practiced other than as particularly described and still
be within the scope of the accompanying claims.
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